Optimal operation of conformal silica deposition reactors

ABSTRACT

Methods of forming conformal films that reduce the amount of metal-containing precursor and/or silicon containing precursor materials required are described. The methods increase the amount of film grown following each dose of metal-containing and/or silicon-containing precursors. The methods may involve introducing multiple doses of the silicon-containing precursor for each dose of the metal-containing precursor and/or re-pressurizing the process chamber during exposure to a dose of the silicon-containing precursor. The methods of the present invention are particularly suitable for use in RVD processes.

CROSS-REFERENCE TO RELATED APPLICATION

This application is related to U.S. patent application Ser. No.11/077,198, filed Mar. 9, 2005.

FIELD OF THE INVENTION

This invention pertains to methods for forming high density, conformal,silica nanolaminate films. More specifically, the invention pertains tomethods of depositing a conformal film of dielectric material onsemiconductor substrates and in structures of confined geometry such ashigh aspect ratio gaps.

BACKGROUND OF THE INVENTION

Layers of dielectric film are used in several applications in sub-micronintegrated circuits (ICs) fabrication. Four such applications areshallow trench isolation (STI), premetal dielectric (PMD), inter-metaldielectric (IMD) and interlayer dielectric (ILD). All four of theselayers require silicon dioxide films that fill features of various sizesand have uniform film thicknesses across the wafer.

Chemical vapor deposition (CVD) has traditionally been the method ofchoice for depositing conformal silicon dioxide films. However, asdesign rules continue to shrink, the aspect ratios (depth to width) offeatures increase, and traditional CVD techniques can no longer provideadequately conformal films in these high aspect ratio features.

Two alternatives to CVD are atomic layer deposition (ALD) and rapidvapor deposition (RVD). ALD methods involve self-limiting adsorption ofreactant gases and can provide thin, conformal dielectric films withinhigh aspect ratio features. ALD methods have been developed for thedeposition of silicon oxide film. RVD processing (also known as pulseddeposition layer (PDL) processing) is similar to ALD in that reactantgases are introduced alternately over the substrate surface. AnALD-based dielectric deposition technique typically involves adsorbing ametal containing precursor onto the substrate surface, then, in a secondprocedure, introducing a silicon oxide precursor gas. The silicon oxideprecursor gas reacts with the adsorbed metal precursor to form a thinfilm of metal-doped silicon oxide. In RVD the silicon oxide film cangrow more thickly. Thus, RVD methods allow for rapid film growth similarto using CVD methods but with the film conformality of ALD methods.

The cost of chemicals needed to deposit a given amount of oxide isinversely proportional to reactant conversion. Reactant conversion in aRVD reactor is typically significantly lower than one and is dependenton process conditions. Thus, in conventional RVD (and ALD) reactors, asignificant amount of the silicon-containing precursor is not utilized.Because conformal deposition processes require reactants of high purity,recovering the silicon-containing precursor in a recycle stream isimpractical. Unreacted precursor is lost. In addition, the amount ofoxide deposited for a given dose of metal-containing precursor islimited, requiring more metal-containing precursor.

What is therefore needed are improved methods for forming conformalfilms that reduce the amount of metal-containing precursor and/orsilicon-containing precursor required to deposit a given amount of filmon a substrate.

SUMMARY OF THE INVENTION

The present invention meets these needs by providing methods of formingconformal films that reduce the amount of metal-containing and/orsilicon containing precursor materials required. The methods of thepresent invention increase the amount of film grown following each doseof metal-containing precursor. In some embodiments, the methods of thepresent invention increase conversion of the silicon-containingprecursor. The methods may involve introducing multiple doses of thesilicon-containing precursor for each dose of the metal-containingprecursor and/or re-pressurizing the process chamber during exposure toa dose of the silicon-containing precursor. The methods of the presentinvention are particularly suitable for use in RVD processes.

One aspect of the invention relates to methods of filling a gap on asemiconductor substrate involving including multiple doses of thesilicon-containing precursor for each dose of the metal-containingprecursor. The methods involve providing a semiconductor substrate in ametal-containing precursor dose chamber, exposing the substrate surfaceto a dose of a metal-containing precursor gas to form a saturated layerof metal-containing precursor on the substrate surface, providing thesubstrate in a silicon-containing precursor dose chamber, exposing thesubstrate surface to a silicon-containing precursor gas, evacuating thesilicon-containing precursor dose chamber and prior to exposing thesubstrate surface to any subsequent doses of the metal-containingprecursor gas, repeating the steps of exposing the substrate to asilicon-containing precursor gas and evacuating the silicon-containingprecursor dose chamber.

According to various embodiments, the steps of exposing the substrate toa silicon-containing precursor gas and evacuating the silicon-containingdose chamber may be repeated multiple times prior to exposing thesubstrate to any subsequent doses of the metal-containing precursor. Inpreferred embodiments, the steps are repeated from 2 to 10 times.

In some embodiments, the substrate may then be exposed again to themetal-containing precursor, and the process repeated until the gap issubstantially filled. In some embodiments, the gap may be substantiallyfilled after exposure to no more than a certain number ofmetal-containing precursor doses. For example, in some embodiments,filling the gap may require no more than four doses of themetal-containing precursor.

In some embodiments, the silicon-containing precursor is at high partialpressure at the beginning of the deposition reaction. In a preferredembodiment, the partial pressure of the silicon-containing precursor gasis at least 10 Torr. In some embodiments, the substrate is exposed thesilicon-containing precursor gas for a time ranging from about 5 to 30seconds.

The metal-containing precursor dose chamber and the silicon-containingprecursor dose chamber may be the same chamber or different chambers. Ina preferred embodiment, they are different chambers.

Another aspect of the invention relates to methods of filling a gap on asemiconductor substrate involving re-pressurizing the reactor chamberduring deposition. The methods involve providing a semiconductorsubstrate in a metal-containing precursor dose chamber, exposing thesubstrate surface to a dose of a metal-containing precursor gas to forma saturated layer of metal-containing precursor on the substratesurface, providing the semiconductor substrate to a silicon-containingprecursor dose chamber, exposing the substrate to a silicon-containingprecursor gas, re-pressurizing the silicon-containing precursor dosechamber; and after re-pressurizing, again exposing the substrate to thesilicon-containing precursor gas.

According to various embodiments, re-pressurizing the silicon-containingprecursor dose chamber may increase the chamber pressure by at least 10Torr and/or by a factor of 1.5–5. In some embodiments, re-pressurizingthe chamber involves introducing a gas selected from an inert gas,oxygen and silane into the chamber. Inert gases are preferred, withnitrogen is particularly preferred.

According to various embodiments, the substrate may be exposed to thesilicon-containing precursor gas prior to re-pressurization from a timeranging from 5–30 seconds, and preferably 5–15 seconds. The substratemay be exposed to the silicon-containing precursor gas afterre-pressurization from a time ranging from 5–30 seconds, and preferably5–15 seconds.

In some embodiments, the method may include, prior to exposing thesubstrate to any subsequent doses of the metal-containing precursor,repeating the steps of exposing the substrate to the silicon-containingprecursor gas, re-pressurizing the chamber, and exposing the substrateto the silicon-containing precursor gas after re-pressurization.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a flowchart depicting the process flow of a method of fillinggaps on a semiconductor substrate in accordance with a conventional RVDprocess.

FIG. 2 is a graph depicting silica growth and TPOSL conversion asfunctions of TPOSL partial pressure and dose time for a conventional RVDprocess.

FIG. 3 is a graph depicting reaction rate and gas phase compositionchanges as functions of TPOSL exposure time in a conventional RVDprocess.

FIG. 4 is a flowchart depicting the process flow of a method of fillinggaps on a semiconductor substrate in accordance with one embodiment ofthe present invention.

FIG. 5 is a graph depicting film growth per cycle and film growth perTPOSL dose as functions of the number of TPOSL doses per cycle for anRVD process in accordance with one embodiment of the invention.

FIG. 6 is a flowchart depicting the process flow of a method of fillinggaps on a semiconductor substrate in accordance with one embodiment ofthe present invention.

FIG. 7 is a graph comparing oxide growth per TPOSL dose for a processwithout re-pressurization and for a process according to one embodimentof the present invention.

FIG. 8 is a flowchart depicting the process flow of a method of fillinggaps on a semiconductor substrate in accordance with one embodiment ofthe present invention.

FIG. 9 is a block diagram depicting various reactor components arrangedfor implementing the deposition of dielectric films in the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the present invention, numerousspecific embodiments are set forth in order to provide a thoroughunderstanding of the invention. However, as will be apparent to thoseskilled in the art, the present invention may be practiced without thesespecific details or by using alternate elements or processes. In otherinstances well-known processes, procedures and components have not beendescribed in detail so as not to unnecessarily obscure aspects of thepresent invention.

As indicated, the present invention provides methods of formingconformal films with increased efficiency. The methods may be used withconformal film deposition techniques such as RVD and ALD. The methodsare particularly suited for used with RVD.

Generally, conventional RVD methods involve sequentially depositing aplurality of atomic-scale films on a substrate surface by sequentiallyexposing and removing reactants to and from the substrate surface.First, a metal-containing precursor gas is injected into a chamber andthe molecules of the gas are chemically or physically adsorbed to thesurface of a substrate, thereby forming a “saturated layer” of themetal-containing precursor. Typically, the remaining gas in the chamberis then purged using an inert gas. Thereafter, a silicon-containingprecursor gas is injected so that it comes in contact with the adsorbedlayer of the metal-containing precursor and reacts to form a reactionproduct. Because the saturated layer of the metal-containing precursoris nominally thin and evenly distributed over the substrate surface,excellent film step coverage can be obtained. The substrate is exposedto a silicon-containing precursor for a period of time sufficient forsilica film to grow to thickness in excess of one monolayer. Furthercycles of substrate exposure to the metal-containing precursor, followedby exposure to the silicon-containing precursor, can be implemented andrepeated as needed for multiple layers of material to be deposited.

Another deposition technique related to RVD is ALD. RVD and ALD are bothsurface-controlled reactions involving alternately directing thereactants over a substrate surface. Conventional ALD, however, dependson self-limiting typically monolayer producing reactions for bothreactant gases. As an example, after the metal-containing precursor isadsorbed onto the substrate surface to form a saturated layer, thesilicon-containing precursor is introduced and reacts only with theadsorbed metal-containing precursor. In this manner, a very thin andconformal film can be deposited. In RVD, as previously described, afterthe metal-containing precursor is adsorbed onto the substrate surface,the silicon-containing precursor reacts with the adsorbedmetal-containing precursor and is further able to react to accumulate aself-limiting, but much thicker than one monolayer film. Thus, as statedpreviously, the RVD process allows for rapid film growth similar tousing CVD methods but with the conformality of ALD type methods.

The differences between conventional ALD and RVD film formation areprincipally due to the difference between the thicknesses of the filmsformed after the completion of each type of process and arise from thenature of the metal-containing species used in the initial layer. InALD, a single exposure to the metal-containing precursor leads to theformation of a monolayer of the product film (generally less than 5 Åthick), while in RVD, the metal-containing precursor catalyzes formationof more than a monolayer of silica film. The typical growth is greaterthan 150 Å/cycle. Typically, a silica RVD process utilizestrimethyaluminum (TMA) as the process aluminum precursor.

The present invention will now be described in detail, primarily withreference to RVD processes for the deposition component of the gap fillprocess. It should be understood that ALD processes may also be used forgap fill in accordance with the invention. Relevant details of ALDprocesses in general are described in M. Ritala and M. Leskela, “Atomiclayer deposition”, Chapter 2, Handbook of thin film materials, vol. 1,“Deposition and processing of thin films”, Hari Singh Nalwa, Ed.(Academic Press, 2002). Given these details and the description providedherein, one of skill in the art would be able to implement the ALDaspect of the invention.

FIG. 1 is a flow chart depicting a conventional RVD process. The process100 starts with a substrate being provided to a metal-containingprecursor dose chamber (101). A metal-containing precursor is thenintroduced to the chamber (103). The substrate is exposed to themetal-containing precursor so that the metal-containing precursor isadsorbed onto the substrate surface (105).

Generally, separate chambers are used for the exposure to themetal-containing precursor in operations 103 and 105 and exposure to thesilicon-containing precursor in the following operations. Thus, thesubstrate is then transferred to a silicon-containing precursor dosechamber (107). The silicon-containing precursor is then introduced tothe silicon-containing precursor dose chamber (109) and the substrate isexposed to the silicon-containing precursor in order for a silicon oxidefilm to be deposited on the substrate (111). Generally the substrate isexposed to the silicon-containing precursor until the reaction stops andfilm is no longer deposited. Exposure to the metal-containing precursorand the silicon-containing precursor described in operations 101–111constitute one cycle of the RVD process. Multiple cycles are thenperformed until the desired amount of film is deposited (for example, tofill a gap on the substrate) (113). Each cycle begins by transferringthe substrate to the metal-containing precursor dose chamber.

As discussed above, the RVD reaction is self-limiting. This can be seenin FIG. 2, which shows film growth and silicon-containing precursor(tris(tert-pentoxy)silanol (TPOSL)) conversion as functions of TPOSLdose time in a conventional RVD process for TPOSL partial pressures of 5Torr and 11 Torr. For a particular partial pressure, the film growth andreactant conversion are constant with respect to dose time. (Althoughexperimental error is not shown on the graph, variations in the filmgrowth and reactant conversion for different dose times are within theexperimental error). For the conventional RVD operation used to generatedata in FIG. 2, a TPOSL dose time of 54 seconds per cycle results in thesame film growth and reactant conversion as a dose time of 4 seconds percycle.

As discussed above, the silicon-containing precursor reacts with theadsorbed metal-containing precursor and reacts further to accumulate afilm. The reaction of the silicon-containing precursor produces the filmas well as byproducts. One commonly used silicon-containing precursor istris(tert-pentoxy)silanol or TPOSL, the molecular formula of which is(C₅H₁₁O)₃SiOH. The reaction of TPOSL to form silicon oxide film is shownbelow:(C₅H₁₁O)₃SiOH→SiO₂+2H₂O+3C₅H₁₀Thus, water and cyclopentene (C₅H₁₀) gas are byproducts of thedeposition reaction. Other byproducts are produced including alcoholsand other hydrocarbons. The metal-containing precursor may beincorporated into the film; for example, aluminum oxide may beincorporated into the film when an aluminum-containing precursor isused.

A recognized reaction limiting mechanism is the inhibition of diffusionof the precursor to the catalytic sites on the adsorbed layer ofmetal-containing precursor. Diffusion of the silicon-containingprecursor is inhibited by cross-linking between molecules of thedeposited film. If diffusion inhibition were the sole rate-controllingmechanism, as previously believed, adsorption of another layer ofmetal-containing precursor would be required to grow more film.

While the diffusion inhibition described above is believed to be onemechanism of limiting the deposition reaction, it is believed thatanother important reaction-limiting mechanism that has not beenpreviously recognized is the inhibition of growth by the reactionbyproducts. Without being bound by a particular theory, it is believedthat byproducts of the silicon oxide producing reaction (e.g., of TPOSLto SiO₂ shown above) are adsorbed onto the catalytic precursor sites,thereby inhibiting the deposition of silicon oxide.

Evidence of this is found by examining enthalpies of adsorption ofprecursor and byproducts on the catalytic sites. For example,isopropanol and water are byproducts in a deposition reaction with atris(isopropoxy)silanol precursor. In a simulation of a depositionreaction, the enthalpies of adsorption on aluminum sites of an adsorbedaluminum-containing precursor were determined to be:water=35.6 kcal/molisopropanol=37.5 kcal/moltris(isopropoxy)silanol=37.8 kcal/molThe difference in enthalpies of adsorption of the silicon-containingprecursor and the reaction byproducts on aluminum sites is less than 2.5kcal/mol. This indicates that deposition of silicon oxide on themetal-containing precursor layer competes with adsorption of thebyproducts on metal-containing precursor sites. The byproducts inhibitreactant conversion.

FIG. 3 shows results of modeling reaction rate and gas phase compositionchanges as functions of TPOSL dose in a conventional RVD process.Reaction rate, TPOSL partial pressure and byproduct partial pressure areshown. Conditions in the reactor reach steady state in less than asecond of dose time, with the reaction rate falling to zero, and TPOSLpartial pressure leveling off at a partial pressure of about 8.2 Torrfrom an initial pressure of about 11 Torr. Byproduct pressure levels offat about 13 Torr. Although not shown in FIG. 3, the model predicted aTPOSL conversion of 24% and 80 Å film growth per cycle, in agreementwith the experimental results obtained for an initial TPOSL partialpressure of 11 Torr shown in FIG. 2. Exact values of reactantconversion, film growth and time for the reaction rate to reach zero aredependent on the particular process conditions. However, FIG. 3demonstrates that for any conventional RVD process, the reaction ratefalls to zero once byproduct partial pressure has reached a certainlevel.

PROCESSES

The methods of the present invention reduce the amount ofmetal-containing precursor and/or silicon containing precursor materialsrequired to grow a given amount of oxide on a substrate.

In some embodiments, the methods of the invention include introducingmultiple doses of the silicon-containing precursor for each cycle. Aprocess flow for illustrating the steps of a method according to onesuch embodiment is depicted in FIG. 4. The process 400 starts with asubstrate being provided to a catalyst dose chamber (401). Themetal-containing precursor is then introduced to the chamber (403). Thesubstrate is exposed to the metal-containing precursor so that themetal-containing precursor is adsorbed onto the substrate surface (405).In the embodiment shown in FIG. 4, separate chambers are used for theexposure to the metal-containing precursor and exposure to thesilicon-containing precursor. Thus, the substrate is then transferred toa silicon-containing precursor dose chamber (407). Thesilicon-containing precursor is then introduced to the dose chamber(409) and the substrate is exposed to the silicon-containing precursorin order for a silicon oxide film to be deposited on the substrate(411). Up until this point, the process 400 is the same as aconventional RVD process as described in FIG. 1. According thisembodiment, the silicon-containing precursor dose chamber is evacuated(413). An evacuation with a pump purge as is well known in the art maybe used. After the reactor is evacuated, the operations 411 and 413 arerepeated N times (415). N is the number of doses of silicon-containingprecursor material per cycle. N may be a predetermined number, forexample, 2, 3, 4, 5, 6, etc. For example, if N is 3, the substrate isexposed to three doses of the silicon-containing precursor per cycle. Inother embodiments, the silicon-containing precursor dosing and chamberevacuation steps may be repeated until the film reaches a certainthickness, rather than a predetermined number. Steps 401–415 constituteone cycle of the RVD process according to this embodiment. Multiplecycles are then performed until the desired amount of film is deposited(for example, to fill a gap on the substrate) by repeating steps 401–415(417).

The process described in FIG. 4 reduces the number of metal-containingprecursor doses required to deposit a given amount of film. There areseveral benefits resulting from this. First, the amount ofmetal-containing precursor required to deposit the required amount offile (e.g. to fill a gap) is reduced. As the metal-containing precursormay contribute significantly to the cost of operation of the process, itis desirable to limit the amount of precursor used. Second, as discussedabove, exposure to the metal-containing precursor and thesilicon-containing precursor typically occur in different chambers,requiring wafer transfer for each metal-containing precursor dose.Reducing the number of metal-containing precursor doses reduces thenumber of transfer operations. Third, the amount of aluminumincorporated into the dielectric film is lowered.

The optimal number doses per cycle may be found by determining the filmgrowth per cycle and per dose of silicon-containing precursor. FIG. 5 isa graph depicting film growth per cycle and film growth per TPOSL doseas a function of the number of TPOSL doses per cycle for an RVD process.Although the results depicted in FIG. 5 are for a particular set ofprocess conditions, the general trends apply to other processconditions. Film growth per dose of TPOSL decreases with successivedoses of TPOSL. For example, for the process shown in FIG. 5, the thirddose of TPOSL results in about 65 Å of film growth, while the thirteenthdose results in less than 30 Å. Thus, the film growth per cycle levelsoff as the number of doses increases, as can be seen in FIG. 5. For aparticular process, an optimal number of doses may be determined. InFIG. 5, for example, a trendline was plotted to determine the optimalnumber of doses for the particular process used to generate the filmgrowth data. Line 501 indicates that for this process the optimal numberof TPOSL doses per cycle is three. The slope of the film thickness curveis constant until about three cycles, after which point it decreases. Asthe number of doses per cycle increases, the amount ofsilicon-containing precursor relative to the amount to metal-containingprecursor increases. The optimal number may depend on other factors suchas the relative cost of the silicon-containing precursor to themetal-containing precursor, as well as on the conditions of theparticular process.

Another aspect of the invention involves increasing the utilization ofthe silicon-containing precursor. In some embodiments, this isaccomplished by re-pressurizing the RVD reaction chamber during exposureto the silicon-containing precursor. FIG. 6 is a flowchart depicting theprocess flow of one embodiment of a method of filling gaps on asemiconductor substrate where the RVD chamber is re-pressurized duringwafer exposure to the silicon-containing precursor. The first steps ofthe process 600 are identical to those described in FIG. 1, with asubstrate being provided to a catalyst dose chamber (601). Themetal-containing precursor is then introduced to the chamber (603). Thesubstrate is exposed to the metal-containing precursor so that themetal-containing precursor is adsorbed onto the substrate surface (605).The substrate is then transferred to a silicon-containing precursor dosechamber (607). The silicon-containing precursor is then introduced tothe dose chamber (609) and the substrate is exposed to thesilicon-containing precursor in order for a silicon oxide film to bedeposited on the substrate (611). Up until this point, the process 600is the same as the RVD process as described in FIG. 1. According thisembodiment, the silicon-containing precursor dose chamber isre-pressurized (613). The chamber may be re-pressurized by introducing agas such as an inert gas. After re-pressurization, the substrate isagain exposed to the silicon-containing precursor (615). Multiple cyclesare then performed until the gap is filled or the desired amount of filmis deposited by repeating steps 601–615 (617).

FIG. 7 is a graph comparing oxide growth per TPOSL dose for aconventional RVD process and for a process with re-pressurization. Thefirst two bars on the graph show oxide growth for 15 seconds and 30seconds of TPOSL exposure. 15 seconds of exposure resulted in 150Å/cycle of oxide deposited. Increasing the exposure time to 30 secondsdid not result in any additional oxide film deposited. This indicatesthat for the particular process conditions used, the deposition reactionrate reached zero by an exposure time of 15 seconds. The third orrightmost bar on graph shows the same process conditions, but with 15seconds of exposure followed by re-pressurization the chamber with 14Torr N₂, followed by another 15 seconds of exposure. Re-pressurizationalmost doubled the film growth per cycle, from 150 Å/cycle to 280Å/cycle. Thus, re-pressurization increases conversion of thesilicon-containing precursor.

Without being bound by a particular theory, it is believed thatre-pressurization displaces the silicon-containing precursor from thevolume behind the showerhead, thereby increasing the concentration ofsilicon-containing precursor above the substrate. Over 80% of the volumein a RVD reaction chamber may sit behind a showerhead. Introducing theN₂ pulse displaces precursor molecules that otherwise would have to relyon diffusion from this volume to reach the substrate surface.

According to various embodiments, the methods of the invention mayinclude introducing multiple doses of the silicon-containing precursorper cycle (as shown in FIG. 4) and re-pressurizing the chamber duringexposure to each dose of the silicon-containing precursor (as shown inFIG. 6). One such embodiment is depicted in the process flow chart inFIG. 8. The process 800 starts with a substrate being provided to ametal-containing precursor dose chamber (801). The metal-containingprecursor is then introduced to the chamber (803). The substrate isexposed to the metal-containing precursor so that the metal-containingprecursor is adsorbed onto the substrate surface (805). The substrate isthen transferred to a silicon-containing precursor dose chamber (807).The silicon-containing precursor is introduced to the chamber (809) andthe substrate is exposed to the silicon-containing precursor in orderfor a silicon oxide film to be deposited on the substrate (811). Thereactor chamber is re-pressurized (813). After re-pressurization, thesubstrate is again exposed to the silicon-containing precursor (815).The silicon-containing precursor dose chamber is then evacuated (817).Operations 809–817 are repeated N times (819), with N being the numberof doses of silicon-containing precursor material per cycle. Multiplecycles are then performed until the desired amount of film is deposited(for example, to fill a gap on the substrate) by repeating steps 801–819(821).

APPARATUS

FIG. 9 is a block diagram depicting some components of a suitablereactor for performing a deposition process in accordance with thisinvention. Note that this apparatus may be used for ALD or RVD processesand is only an example of suitable apparatus in accordance with thepresent invention. Many other apparatuses and systems, including amulti-chambered apparatus as discussed above, may be used.

As shown, a reactor 901 includes a process chamber 903, which enclosescomponents of the reactor and serves to contain the reactant gases andprovide and area to introduce the reactant gases to substrate 909. Thechamber walls may be made of or plated with any suitable material,generally a metal that is compatible with the deposition and associatedprocesses conducted therein. In one example, the process chamber wallsare made from aluminum. Within the process chamber, a wafer pedestal 907supports the substrate 909. The pedestal 907 typically includes a chuck908 to hold the substrate in place during the deposition reaction. Thechuck 908 may be an electrostatic chuck, a mechanical chuck or variousother types of chuck as are available for use in the industry and/orresearch. The pedestal comprises resistive heating elements. Thereactant gases, as well as inert gases during purge, are introducedindividually into the reactor at tube 925 via inlet 917. A showerhead927 may be used to distribute the gas flow uniformly in the processreactor. Reactant gases are introduced through a gas supply inletmechanism including orifices. There may be multiple reactant gas tubesand inlets. A vacuum pump connected to outlet 919 can draw out gasesbetween RVD cycles. Precursor gas may be supplied from a reservoir 929that may hold the gas at the desired pressure until it is supplied tothe chamber. Vaporizer 931 may vaporize the precursor before it issupplied to the chamber.

PROCESS PARAMETERS

Metal-containing Precursors

Examples of metal-containing precursors include aluminum, zirconium,hafnium, gallium, titanium, niobium, or tantalum compounds. Inembodiments wherein RVD is employed, the metal-containing precursor is atransition metal precursor, preferably an aluminum-containing precursor,capable of aiding the catalytic polymerization of the subsequently addedsilicon-containing precursor to produce a film thicker than a monolayer.In some preferred embodiments, for example,hexakis(dimethylamino)aluminum (Al₂(N(CH₃)₂)₆) or trimethylaluminum(Al(CH₃)₃) are used. Other suitable aluminum-containing precursorsinclude, for example, triethylaluminum (Al(CH₂CH₃)₃) or aluminumtrichloride (AlC1 ₃). Exposure times suitable for forming a saturatedlayer are typically only seconds.

Silicon-containing Precursors

In embodiments wherein RVD is employed, the silicon-containing precursorshould be capable of polymerization when exposed to the adsorbedaluminum-containing precursor to produce a film thicker than amonolayer. Preferred silicon-containing precursors include silanols andsilanediols, such as alkoxysilanols, alkyl alkoxysilanols, alkylalkoxysilanediols and alkoxysilanediols. Examples of suitable precursorsinclude tris(tert-butoxy)silanol ((C₄H₉O)₃SiOH),tris(tert-pentoxy)silanol((C₅H₁₁O)₃SiOH), di(tert-butoxy)silandiol((C₄H₉O)₂Si(OH)₂), tris(isopropoxy)silanol and methyldi(tert-pentoxy)silanol.

Other gases may be introduced to the chamber with the silicon-containingprecursor gas. Such gases include an oxygen source and/or a hydrolyzingagent. Examples of oxygen sources include O₂, O₃, H₂O₂, NO₂, N₂O₃, N₂O₅or HNO₃. Examples of hydrolyzing agents are compounds containinghydrogen with some protoic character such as H₂O or H₂O₂, H₃PO₄, HF orHCl. Additionally, any dopant gas may be introduced, includingphosphorous-, fluorine- and carbon-containing dopant gases. A carriergas may also be used. Typically the carrier gas is an inert gas.

Temperature and Pressure

Chamber pressure in conventional RVD processes is typically between 500mTorr and 2 Torr. However, in a preferred embodiment, thesilicon-containing precursor gas is at a high partial pressure. FIG. 1shows that higher silanol conversion and film growth is obtained for apartial pressure of 11 Torr than for a partial pressure of 5 Torr. Thepartial pressure of the silicon-containing precursor gas may be as highas 200 Torr. In preferred embodiments, the partial pressure is betweenabout 10 Torr and 40 Torr. In a particularly preferred embodiment of thepresent invention, the partial pressure of thesilicon-containing-precursor gas is about 10 Torr. Deposition of thesilicon-containing precursor at high partial pressure is described inU.S. patent application Ser. No. 11/026,284, filed Dec. 30, 2004, whichis hereby incorporated by reference in its entirety. Partial pressure asused above refers to the partial pressure of the silicon-containingprecursor at the onset of the deposition reaction.

In some embodiments wherein multiple doses of the silicon-containingprecursor per cycle are introduced, the partial pressure of thesilicon-containing precursor may be increased from dose to dose.

Wafer temperatures as used for standard conformal film depositionprocesses may be used in the methods of the present invention. Inpreferred embodiments wherein the metal-containing precursor is analuminum-containing precursor, the temperature of the substrate isbetween about 150° C. and 250° C. during exposure to themetal-containing precursor. In particularly preferred embodiments, thetemperature of the substrate is between about 150° C. and 200° C.

In preferred embodiments wherein the silicon-containing precursor is asilanol, the temperature of the substrate is between about 200° C. and300° C. during exposure to the silanol. In a particularly preferredembodiment, the temperature is between about 225° C. and 300° C. In aneven more particularly preferred embodiment, the temperature is betweenabout 250° C. and 300° C.

Exposure Time

The substrate should not be exposed to the silicon-containing precursorafter the deposition reaction has stopped. The optimal exposure time isa function of particular process conditions including temperature andpressure. In some embodiments exposure times may range from 5–30seconds.

Re-pressurization

The reactor chamber may be re-pressurized during exposure to thesilicon-containing precursor by introducing a gas to the chamber.Suitable gases include N₂, Ar, He, other inert gases, O₂, a dopant gasor silane. In a preferred embodiment, the chamber is re-pressurized withan inert gas.

In some embodiments, the re-pressurization increases the chamberpressure by 1.5–5 times. In some embodiments, the re-pressurization mayincrease the pressure by at least 10 Torr.

OTHER EMBODIMENTS

This method applies to the deposition of silica (USG). However, thismethod may also be used for depositing doped silica films, such asfluorine-doped silicate glass (FSG), phosphosilicate glass (PSG),boro-phospho-silicate glass (BPSG), or carbon doped low-k materials.

Other deposition co-reactants, such as silanols with varyingsubstituents (e.g., more than one kind of alkoxy substituent) may beused to improve the film characteristics. For an example, see U.S.patent application Ser. No. 10/874,814, filed Jun. 22, 2004, titled“Mixed Alkoxy Precursors and Methods of Their Use for Rapid VaporDeposition of SiO₂ Films.” Furthermore, the properties of the dielectricfilm may be improved by other means as well, including by using analuminum oxide nucleation layer formed by ALD prior to the applicationof the silica layer. See, for example, U.S. patent application Ser. No.10/875,158, filed Jun. 22, 2004, titled “Silica Thin Films Produced ByRapid Surface Catalyzed Vapor Deposition (RVD) Using a NucleationLayer.” Note also that this technique may be used in combination with aphosphorous-containing film as described in U.S. patent application Ser.No. 10/874,808, filed Jun. 22, 2004, titled “Aluminum PhosphateIncorporation In Silica Thin Films Produced By Rapid Surface CatalyzedVapor Deposition (RVD).” The above-referenced applications areincorporated by reference in their entirety for all purposes.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing both the process and apparatus of the present invention.Accordingly, the present embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalents of the appended claims.

1. A method of filling a gap on a semiconductor substrate, the methodcomprising: a) providing a semiconductor substrate in a metal-containingprecursor dose chamber; b) exposing the substrate surface to a dose of ametal-containing precursor gas to form a saturated layer ofmetal-containing precursor on the substrate surface; c) providing thesemiconductor substrate in a silicon-containing precursor dose chamber;and d) introducing a dose of silicon-containing precursor gas to thechamber; and e) after the dose is introduced to the chamber, exposingthe substrate to the dose of the silicon-containing precursor gas suchthat the gas reacts with the saturated layer of metal-containingprecursor to deposit silicon oxide; wherein (e) is completed prior tointroducing a subsequent dose of silicon-containing precursor gas and(e) comprises: (i) exposing the substrate to the dose of thesilicon-containing precursor gas for a first period of time (ii)re-pressurizing the silicon-containing precursor dose chamber duringexposure to the dose of the silicon-containing precursor gas, therebyincreasing the pressure in the chamber; and (iii) after re-pressurizing,exposing the substrate to the dose of the silicon-containing precursorgas for a second period of time.
 2. The method of claim 1, furthercomprising repeating steps (a)–(e) until the gap is substantiallyfilled.
 3. The method of claim 1, wherein step (ii) comprises increasingthe chamber pressure by at least 10 Torr.
 4. The method of claim 1,wherein step (ii) comprises increases the chamber pressure by a factorof 1.5–5.
 5. The method of claim 1, wherein step (ii) comprisesintroducing a gas selected from nitrogen, argon, helium and oxygen intothe chamber.
 6. The method of claim 5, wherein step (ii) comprisesintroducing nitrogen into the chamber.
 7. The method of claim 1, whereinthe first period of time ranges from about 5 to 15 seconds.
 8. Themethod of claim 1, wherein the second period of time ranges from about 5to 15 seconds.
 9. The method of claim 1, wherein the silicon-containingprecursor is at least one of tris(tert-butoxy)silanol,tris(tert-pentoxy)silanol, di(tert-butoxy)sinlandiol and methyldi(tert-pentoxy)silanol.
 10. The method of claim 1, wherein thetemperature of the substrate is between about 200° C. and 300° C. duringexposure to the silicon-containing precursor gas.
 11. The method ofclaim 10, wherein the temperature of the substrate is between about 150°C. and 250° C. during exposure to the metal-containing precursor gas.12. The method of claim 1, wherein the metal-containing precursor is analuminum-containing precursor.
 13. The method of claim 12, wherein thealuminum-containing precursor is at least one of hexakis(dimethylamino)aluminum, trimethylaluminum, triethylaluminum and aluminum trichloride.14. The method of claim 13, wherein the aluminum-containing precursor istrimethyl aluminum.
 15. The method of claim 1, wherein the partialpressure of the silicon-containing gas at the beginning of step (d) isequal to or greater than about 10 Torr.
 16. The method of claim 1,further comprising: f) prior to exposing the substrate surface to anysubsequent doses of the metal-containing precursor gas, repeating step(d) and (e).